Numbers 15:39-40

It shall be a (blue) tassel for you to look at and remember all the commandments of the Lord, to do them, so that you do not follow after (the desires of) your own heart and eyes, (desires) after which you used to follow and play the prostitute, so that you may remember to do all My commandments and be holy (set apart) to your God.

We need reminders in our lives not to be willfully disobedient to God. The devil is sneaky, enticing, and constantly trying to attract our eyes to turn away from God. If we remain on guard and turn away from distractions, we will keep ourselves set apart for God. It matters where we focus and keep our guard up.